A man and a woman both have brown eyes, but their first child has blue eyes. Wha
ID: 3456790 • Letter: A
Question
A man and a woman both have brown eyes, but their first child has blue eyes. What are the chances that their second child will have blue eyes? Jane is blood type A and her husband is blood type B. Jane is puzzled because their daughter is type O. Explain how the daughter inherited a blood type neither of her parents has.
Jim is blood type A and his mother is blood type O. What are the possible blood types of his father? (Three answers)
Jack is a hemophiliac (sex linked recessive) but his wife is not (sex linked dominant). What are the chances that they will have a child with hemophilia? (Give all possibilities)
Explanation / Answer
The brown eye form of the eye color gene (or allele) is dominant, whereas the blue eye allele is recessive.If both parents have brown eyes yet carry the allele for blue eyes, a quarter of the children will have blue eyes, and three quarters will have brown eyes.So if the parents are carrying a recessive blue eye gene then there is almost 25% chance of the baby having blue eyes. One parent with A and another with B can produce a child with A, B, AB or O blood types.ABO blood types can be complicated to understand. This is mostly due to the fact that the 'O-type' antigen is masked by the presence of an A- or B-type antigen. If Jim has blood type A and his mother O,then the father would have A blood type. And if both parents have A blood type then also the child can have A blood type. Also if father has AB type and mother O then also the child can have A blood type. The hemophilia gene is passed down from parent to a child. The genes for hemophilia A and B are on the X chromosome. For this reason, hemophilia is called an X-linked (or sex-linked) disorder. When the father has hemophilia but the mother does not, none of the sons will have hemophilia. All the daughters will carry the hemophilia gene.The father's sex chromosomes are labeled XY, with the X chromosome carrying the hemophilia gene. The father only passes half of his sex chromosomes to the baby, either the X or the Y. If the baby gets the Y chromosome from the father it will be a boy. Since the Y chromosome does not carry the hemophilia gene, a son born to a man with hemophilia and a woman who is not a carrier will not have hemophilia. If the baby gets the X chromosome from the father it will be a girl. The X chromosome from the father with hemophilia will have the hemophilia gene. But the girl also gets an X chromosome from her mother. The normal blood clotting gene on the X chromosome from the mother is dominant, so the baby girl will not have hemophilia. She will, however, be a hemophilia carrier since she has the hemophilia gene on one of her X chromosomes.So in this case, all sons born to the couple will be normal and all daughters will be hemophilia carriers
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